<script type="module">
	{
		let s = Symbol();

		document.write(`第7种数据类型：${typeof s}<br><br>`);
		
		var s1 = Symbol('foo');
		var s2 = Symbol('bar');
		
		document.write(`带参数的Symbol：${s1.toString()}<br><br>`);
		document.write(`带参数的Symbol：${s2.toString()}<br><br>`);
	}
</script>